The invention is directed to a device or item to be used for the quelling of the foam action of slag in the basic oxygen process or adjacent vessels which contain molten metal. The word "slag" as employed herein may be considered to be a by-product of the steelmaking process but might have additional application to other types of metals. The relatively recent use of high pressure oxygen to speed the steelmaking process has also occasioned an enormous flow of oxygen bubbles not only into the steel and also into the slag layer or blanket which normally covers it during the melting process to its final composition. The entrapment of the oxygen bubbles, of course, has increased the apparent volume of the slag covering, similar to the froth on a malted milk or foaming glass of freshly poured beer.
In the steelmaking process the time period consumed waiting for the settling of foam in the slag slows down the process. It has become the practice to speedily quell this slag foaming by throwing shovel fulls of salt (NACL) or similar materials to quell the action of the slag and through a gently eruptive process compress the space occupied by the effervescent slag blanket. Regulatory agencies of the federal government such as the Environmental Protection Agency (EPA) and (OSHA) have objected to the by-products of this introduction of salt into the slag on the grounds that it produces noxious fumes and/or other elements which are harmful to the atmosphere and personnel controlling the process.
The device, as disclosed herein, is also intended to reduce the volume of the slag without creating these objectionable fumes or elements that have heretofore occurred through the use of salt, as alluded to above. The device preferably comprises a cylindrical body or tube made out of pasteboard or some similar cellulosic, combustible or burnable material containing a calculated amount of siliceous materials or siliceous aggregate accompanied with a moderate amount of readily ignitible means which may be utilized to promote burning of burnable material.
The device, as presently constructed preferably weighs approximately two pounds, is adapted to be tossed into the mouth of a basic oxygen receptacle, or other vessel at the time when the oxygen lances have been withdrawn with the objective of immediate reduction of the volume occupied by the slag. It may also be used in the adjacent slag thimbles or receptacles which are used to receive slag. Here it performs the same function of reducing the volume of the slag and causes the eruptive discharge of the entrapped oxygen bubbles which are in the slag at that time. It is theorized that the pasteboard or paper laminates afford nothing more than entrapped moisture and offer an avenue for the reaction of the entrapped air to erupt harmlessly into the atmosphere. The contained siliceous aggregate serves to primarily weight the pasteboard tube down to encourage its penetration into the slag blanket to a depth where it will be allowed to work on the surrounding air bubbles and slag and so that the ignitible means will encourage a flame or flames working from the interior of the tube. Caps or closure means at the ends of the tube are known to decompose in the slag and this allows the penetration of the slag with its entrapped oxygen bubbles to work from the inside and thereby encourage reactions simultaneously to promote burning thereof on the outside and inside of the tube. The enclosed siliceous aggregate is released and blends into the slag forming no deleterious chemicals and can be subsequently drained off into vessels provided therefor its final distribution. The caps serve to detain the siliceous material, constituting a weight means in the tube. The device may be designed and constructed in various ways but as presently constructed the use of a combustible or burnable cylindrical tube and sand constituting a weight means has proven to be economical and practical to produce.